1. Field
The present invention relates to a pull-down signal detecting apparatus for detecting a pull-down signal generated from, for example, a cine film, and a pull-down signal detecting method. In addition, the invention relates to an improvement of an interlace-progressive converter using the pull-down signal detecting apparatus.
2. Description of the Related Art
As is generally known, currently, in a video signal of an NTSC (national television system committee) method, a PAL (phase alternation by line color television) method, or the like generally used as a standard television broadcasting method, video is scanned in a so-called interlaced scanning method that a 1-frame video signal is generated in two fields.
In recent, a thin-sized and large-screen television broadcasting receiver using a liquid crystal display and a plasma display has come into wide use. However, when an interlaced scanning video signal is displayed as it is in each scanning line using such a display, brightness of picture decreases and thus invisible video is displayed.
For this reason, in such a display, the interlaced scanning video signal is converted into a progressive scanning video signal and the converted signal is displayed. That is, in such a kind of displays, it is necessary to perform a progressive scanning converting process to convert the interlaced scanning video signal into the progressive scanning video signal.
The video signal based on the video signal the standard television method may include a video signal generated on the basis of the video of the cine film. In this case, since the number of frames at every second in the cine film and the number of frames (the number of fields) at every second in the video signal based on the standard method are set individually, generally, they do not coincide with each other.
For this reason, the video of the cine film is converted into a video signal based on the standard television method according to the interlace scanning, by using a 2-2 pull-down method, 2-3 pull-down method, or the like. The interlaced scanning video signal generated from the cine film as described above is called as a pull-down signal.
However, in the aforementioned progressive scanning converting process, it is possible to improve video quality by changing the method of the conversion process into the progressive scanning method, according to whether or not the input video signal is pull-down signal. Accordingly, it is important to accurately detect whether or not the input video signal is the pull-down signal, at the time of performing the progressive scanning converting process.
In JP-A-2002-330408, there is disclosed a technique that a integration result of difference before and after one field of the present field is determined in the whole fields by a threshold level varied by a level of an APL detector for detecting an average brightness level of an input video signal, and determination of a telecine conversion signal is performed on the basis of the field determination result of the five fields.